System and method for interfacing applications processor to touchscreen display for reduced data transfer

ABSTRACT

System and method for substantially reducing an involvement of an applications processor in receiving data from a touchscreen display. In one aspect, the system includes a controller may be configured in an autonomous mode where it automatically measures the touchscreen display based configuration information received from the applications processor, determines notable events based on the measurement data, stores data and event identifiers related to the notable events in a memory, and sends a notification to the applications processor when event data is available In another aspect, the system includes a controller that filters user interactions events and transmits data related to only notable events to the applications processor. Because of the autonomous and event filtering operations of the touchscreen controller, there are substantially less communications between the controller and the applications processor. This improves the speed and efficiency of the applications processor.

CROSS REFERENCE TO RELATED APPLICATION

This application claims priority to and is a continuation of copendingpatent application Ser. No. 12/620,430, entitled, “System And Method ForInterfacing Applications Processor To Touchscreen Display For ReducedData Transfer,” filed Nov. 17, 2009, which application claims priorityto Provisional Patent Application No. 61/122,269, entitled, “System AndMethod For Interfacing Applications Processor To Touchscreen Display ForReduced Data Transfer,” filed Dec. 12, 2008, which applications arehereby incorporated herein by reference in their entireties.

FIELD

This invention relates generally to controllers for touchscreendisplays, and in particular, to a system and method for interfacing anapplications processor to a touchscreen display in a manner that reducescommunications between the controller and the applications processor.

BACKGROUND

A touchscreen controller is typically employed for interfacing anapplications processor with a touchscreen display. The touchscreencontroller senses interactions of the touchscreen display by the user,and communicates those interactions to the applications processor. Suchinteractions may include initial touching of the display by the user,dragging a pointer or finger across the display, and releasing thepointer or finger from the display. Based on the application, theapplications processor performs one or more operations in response tothe detected interactions.

In the past, the touchscreen controller would communicate all detectableuser interactions or events to the applications processor, no matter howsmall or minute those interactions were. Such operation would result ina large number of communications between the touchscreen controller andthe applications processor. This generally reduced the speed andefficiency of the applications processor in performing userapplications. This is better exemplified with reference to the followingexample.

FIG. 1 illustrates a flow diagram of a method 100 of interfacing anapplications processor with a touchscreen display using a conventionaltouchscreen controller (TSC). According to the method 100, a touchscreencontroller sits in idle mode issuing an interrupt signal IRQ=0indicating that the touchscreen display is not being touched (block102). Then, in response to the touchscreen controller detecting thetouching of the touchscreen display and issuing an interrupt signalIRQ=1 indicating the same, the applications processor sends a request tothe touchscreen controller to perform a measurement of the touchscreendisplay (block 104). In response to the measurement request, thetouchscreen controller performs the requested measurement (block 108),while the applications processor waits a time interval ofT_(MEASUREMENT) for the measurement to be complete (block 106).

Once the measurement has been completed, the applications processorretrieves the measurement data from the touchscreen controller (block110). Then, the applications processor determines whether thetouchscreen display is being touched based on the interrupt signal IRQissued by the touchscreen controller (block 112). If the touchscreendisplay is not being touched as indicated by the interrupt signal IRQ=0,the applications processor causes the touchscreen controller to revertback to idle mode (block 102). On the other hand, if the touchscreendisplay is being touched as indicated by the interrupt signal IRQ=1, theapplications processor waits a time interval T_(SAMPLE) for the nextscheduled measurement cycle (block 114) before requesting anothermeasurement (block 104).]

As apparent from the flow diagram of the method 100, the applicationsprocessor is highly involved in the touchscreen measurement process. Forinstance, for each measurement cycle, the applications processor sends arequest for measurement to the touchscreen controller, retrieves themeasurement data, and determines whether the touchscreen is beingtouched based on the IRQ signal. This involvement consumes a substantialamount of time and resources for the applications processor, which couldbe allocated to other more useful operations, such as user applications.

SUMMARY

An aspect of the invention relates to a system and method of interfacingan applications processor with a touchscreen display or otherposition-indicating device. According to this aspect, a controller maybe configured in an autonomous mode where it automatically measures thetouchscreen display based configuration information received from theapplications processor, determines notable events based on themeasurement data, stores data and event identifiers related to thenotable events in a memory, and sends a notification to the applicationsprocessor when event data is available. The use of such controller andits techniques substantially reduces the involvement of the applicationsprocessor in interfacing with the touchscreen display. For instance, theapplications processor need only to receive notification from thecontroller as to when data is available, and to access the data at itsleisure based on the current user application.

Another aspect of the invention relates to a system and method forreducing data transfer, related to user interaction of a touchscreendisplay or other position-indicating device, between a controller and anapplications processor. In this regard, the controller filters userinteraction events so that data related to only filtered notable userinteractions events are transmitted to the applications processor. Suchnotable events may include initial touches of the touch screen displayby the user, releases or removal of the pointer or finger from thetouchscreen display, and mid-press or dragging of the pointer or fingeracross the touchscreen display that exceeds a defined distance. Becauseof the filtering operation performed by the touchscreen controller,there are substantially less data transfer between the controller andthe applications processor. This improves the speed and efficiency ofthe applications processor.

Other aspects, advantages and novel features of the present inventionwill become apparent from the following detailed description of theinvention when considered in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a flow diagram of a method of interfacing anapplications processor with a touchscreen display using a conventionaltouchscreen controller (TSC).

FIG. 2 illustrates a block diagram of an exemplary system forinterfacing an applications processor with a touchscreen display inaccordance with an embodiment of the invention.

FIG. 3 illustrates a diagram of an exemplary touchscreen displayillustrating an aperture filtering concept in accordance with anotherembodiment of the invention.

FIG. 4 illustrates an exemplary table of recorded touchscreenmeasurement data stored in a first-in-first-out (FIFO) memory in thecase where aperture filtering is enabled in accordance with anotherembodiment of the invention.

FIG. 5 illustrates an exemplary table of recorded touchscreenmeasurement data stored in a first-in-first-out (FIFO) memory in thecase where aperture filtering is not enabled.

FIG. 6 illustrates a flow diagram of an exemplary method of interfacingthe applications processor with the touchscreen display in accordancewith another embodiment of the invention.

FIG. 7A illustrates a flow diagram of another exemplary method ofinterfacing the applications processor with touchscreen display inaccordance with another embodiment of the invention.

FIG. 7B illustrates a flow diagram of an exemplary method of anapplications processor interfacing with a touchscreen controller inaccordance with another embodiment of the invention.

FIG. 7C illustrates a timing diagram related to an exemplary operationof the touchscreen controller in accordance with another embodiment ofthe invention.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

FIG. 2 illustrates a block diagram of an exemplary system 200 forinterfacing an applications processor with a touchscreen display inaccordance with an embodiment of the invention. In summary, the system200 includes a touchscreen controller that may be configured to (1)self-schedule the measurement of the touchscreen display, (2) performthe defined touchscreen measurement, (3) analyze the measurement data todetermine whether it corresponds to a notable event worthy of informingthe applications processor, (4) store the measurement data of thenotable event along with an event tag in a memory, and (5) send anotification to the applications processor when event data in the memoryis available. As an example, the touchscreen controller may identifynotable events as initial touches of the touchscreen display, releasesfrom the touchscreen display, and mid-press drags that exceeds aprogrammable aperture or distance. The touchscreen controller may alsoinform the applications processor when there is no more data availablein the memory.

In particular, the system 200 comprises a touchscreen controller 210, atouchscreen display 250, and an applications processor 260. Thetouchscreen controller 210, in turn, comprises an aperture filter 212,an event filter 214, a first-in-first-out (FIFO) memory 216, a controlmodule 218, a driver/sensor 220, and an applications processor interface222. Although the aperture filter 212 and event filter 214 are shown asseparate items, it shall be understood that their functionality may beincorporated into the control module 218.

As discussed in more detail below, the control module 218 receivesconfiguration instructions from the applications processor 260 by way ofthe interface 222 as to how and when to perform the touchscreenmeasurements and what events should be captured. For example, theconfiguration instructions may inform the touchscreen controller 210 ofthe rate to scan or take measurements of the touchscreen display 250(e.g., every one microsecond (μs) or every 100 milliseconds (ms)), whatone or more measurements to take (e.g., the x-position of the touch, they-position of the touch, the z-position or pressure of the touch, etc.),and what events to record for subsequent access by the applicationsprocessor (e.g., initial touches, mid-press drag that exceeds a definedaperture, touch releases, etc.). In response to these instructions, thecontrol module 218 sets the touchscreen scanning rate of thedriver/sensor 220, the aperture dimensions of the aperture filter 212,and the notable events of the event filter 214.

The control module 218 using the driver/sensor 220 monitors thetouchscreen display 250 in a lower power mode for an initial touch ofthe display by the user. If the control module 218 detects that the userhas initially touched the touchscreen display 250 and the initial touchis a notable event in accordance with the event filter 214, the controlmodule records the corresponding data (e.g., x-, y-, z-position orpressure of the touch) and an event tag (e.g., 00 indicating an initialtouch event) in the FIFO memory 216, and sends an interrupt to theapplications processor 260 via the interface 222. The applicationsprocessor 260 can then retrieve the event parameters from the FIFOmemory 216 at its leisure, and perform one or more program functionsbased on the event parameters. It shall be understood that theapplications processor 260 may retrieve data related to one or moreevents during a single read of the FIFO memory 216.

After the initial touch, the control module 218 using the driver/sensor220 periodically scans the touchscreen display 250 in a higher powermode at the selected scanning rate for user interactions. When notscanning, the control module 218 may be configured in a lower powermode. If the control module 218 senses that the user has dragged apointer or finger across the touchscreen display 250, the control moduledetermines the distances of the drag in the x-direction ΔX and in they-direction ΔY. The control module 218 then sends the ΔX and ΔYinformation to the aperture filter 212. The aperture filter 212 thendetermines whether the ΔX and ΔY exceeds the specified aperturedimensions (e.g., whether ΔX>ΔXa or ΔY>ΔYa, where ΔXa is the absolutedistance between the anchor point and the boundary of the aperture inthe x-direction, and ΔYa is the absolute distance between the anchorpoint and the boundary of the aperture in the y-direction). It shall beunderstood that the aperture may be defined in many other differentmanners.

If the aperture filter 212 determines that the drag of the user'spointer or finger does not exceed the specified aperture dimension, theaperture filter 212 informs the control module 218 that this is not anotable event worthy of informing the applications processor 260. If, onthe other hand, the aperture filter 212 determines that the drag of theuser's pointer or finger exceeds the specified aperture dimension, theaperture filter 212 informs the control module 218 that this is anotable event worthy of informing the applications processor 260. Inresponse, the control module 218 writes the measurement data (e.g., x-,y-, z-position or pressure of the touch) and event tag (e.g. 01indicating a midpress event) in the FIFO memory 216, and sends aninterrupt to the applications processor 260 via the interface 222. Theapplications processor 260 can then retrieve the event parameters fromthe FIFO memory 216 at its leisure, and perform one or more programfunctions based on the event parameters.

The control module 218 using the driver/sensor 220 may sense subsequentdrags of the user's pointer or finger on the touchscreen display 250,and the control module 218 repeats the same process discussed above todetermine whether any one or more of the user's subsequent drags areevents worthy of informing the applications processor 260. The controlmodule 218 may then detect that the user has released its pointer orfinger from the touchscreen display 250, and inform the event filter 214of such. If, in accordance with the event filter 214, the touch releaseis a notable event, the control module 218 records the measurement data(e.g., x-, y-, z-position or pressure of the touch) and event tag (e.g.10 indicating a touch release event) in the FIFO memory 216, and sendsan interrupt to the applications processor 260 via the interface 222.The applications processor 260 can then retrieve the event parametersfrom the FIFO memory 216 at its leisure, and perform one or more programfunctions based on the event parameters.

In contrast to prior touchscreen controllers, the touchscreen controller210 substantially reduces the involvement of the applications processor260 in the operation of the touchscreen display. In essence, theapplications processor 260 has to initially configure the touchscreencontroller 210 as to the measurement criteria (e.g., scan rate, positiondata, etc.) and the data collection criteria (e.g., notable events), beinformed of when data is available, and access the available data fromthe touchscreen controller at its leisure. Additionally, the touchscreencontroller substantially reduces data transfer to the applicationsprocessor 260 by only sending notable events, instead of sending theapplications processor 260 all detectable events regarding userinteractions with the touchscreen display 250. This improves the speedand efficiency of the applications processor 260, allowing it to performmore useful functions instead of communicating with the touchscreencontroller more frequently. These concepts are explained below withreference to the following referenced figures. Although the touchscreendisplay 250 has been used to exemplify the various concepts of theinvention, it shall be understood that the display could be anyposition-indicating device.

FIG. 3 illustrates a diagram of an exemplary touchscreen displayillustrating an aperture filtering concept in accordance with anotherembodiment of the invention. In this example, a rectangular coordinatesystem (24×16 units) is superimposed upon the touchscreen display toillustrate positions in the following exemplary user interaction of thetouchscreen display. Also, in this example, an aperture filter having adimension of plus/minus four (±4) units in the x-direction, andplus/minus four (±4) units in the y-direction has been defined.

According to this example, the user makes an initial touch of thetouchscreen display at position “1” having a coordinate of (7, 11),which is captured during a first measurement of the touchscreen display250 by the touchscreen controller 210. The event filter 214 of thetouchscreen controller 210 causes this event to be recorded in the FIFO216 for subsequent retrieval by the applications processor 260. Thetouching of the display 250 at position “1” causes the aperture filter212 to set up a ±4 by ±4 aperture window APER 1 (boundaries are noted asdashed lines) around the anchor position “1” (e.g., position “1” beingsubstantially in the middle of the aperture filter). It shall beunderstood that the anchor position or point need not be in the middleof the aperture window. Thus, when the touchscreen controller 210 takesthe second measurement of the touchscreen display 250, the user hasdragged the pointer or his/her finger to the coordinate (9, 10) (notedas a solid black circle). The aperture filter 212 does not cause thatevent to be recorded in the FIFO 216 because it did not reach or exceedthe boundary of the aperture window APER 1.

However, in this example, the user dragged the pointer or his/her fingerto position “2” at coordinate (11, 9) when the third measurement of thetouchscreen display 250 took place. Position “2” lies at the boundary ofthe aperture window APER 1. Because the drag now has reached theboundary of the aperture window APER 1, the aperture filter 212 causesthe drag event to be recorded in the FIFO 216. Additionally, theaperture filter 212 sets up a new aperture window APER 2 around anchorposition “2”. Further, in this example, the user has dragged the pointeror his/her finger to position “3” at coordinate (12, 4) when the seventhmeasurement of the touchscreen display 250 took place. The aperturefilter 212 causes the drag to position “3” to be recorded in the FIFO116 because it exceeded the boundary of the aperture window APER2.However, as noted, the aperture filter 212 does not cause theintermediate positions at coordinates (12, 8), (13, 7), and (13, 6)(noted as solid black circles), captured during the fourth, fifth, andsixth measurements of the touchscreen display 250, to be recorded in theFIFO 216 because these points are within the boundary of aperture windowAPER 2.

Similarly, the aperture filter 212 sets up a new aperture window APER3surrounding anchor position “3”. Thus, when the user dragged the pointeror his/her finger to position “4” at coordinate (17, 7) when the ninthmeasurement of the touchscreen display 250 took place, the aperturefilter 212 causes the drag to position “4” to be recorded in the FIFO216, but does not record the intermediate position at coordinate (15, 6)captured during the eight measurement of the touchscreen display 250,since it lies within the aperture window APER3. Further, in thisexample, the user drags the pointer or his/her finger to position “5” atcoordinate (19, 8), and then removes the pointer or his/her finger fromthe touchscreen display 250. The event filter 214 then causes theremoval or release of the pointer or finger to be recorded in the FIFO216, with the event overriding the aperture criteria.

Then, in the example, the user re-touches the touchscreen display 250 atposition “6” with coordinate (22, 14). The event filter 214 causes thisevent to be recorded in the FIFO 216. This causes the aperture filter212 to set up a new aperture window APER 6 surrounding anchor position“6”. Then, the user has dragged the pointer or his/her finger toposition “7” at coordinate (23, 15), and releases or removes the pointeror his/her finger from the touchscreen display 250 detected in the nextmeasurement of the display. Accordingly, the event filter 214 causes therelease or removal to be recorded in the FIFO 216, even though thepositional change does not meet aperture criteria defined by aperturewindow APER 6.

The timing waveform entitled “Interrupt Timing Waveform 1 (assumingfrequent servicing events, w/ aperture)” illustrates that the aboveexemplary user interaction with the touchscreen display resulted in onlyseven (7) interrupts of and data transfer to the applications processor260. On the other hand, without the aperture filter, as illustrated inthe timing waveform entitled “Interrupt Timing Waveform 2 (assumingfrequent servicing events, w/o aperture),” many more interrupts and datatransfers would have been communicated to the applications processor260, which would slow down and reduce the efficiency of the processor.The timing waveform entitled “Interrupt Timing Waveform 3 (assuminginfrequent servicing events)” illustrates that the applicationsprocessor 260 may access the data associated with an event at itsleisure. For example, in this case, the interrupt for event “1” wasissued just after event 1 took place, but the applications processor 260did not retrieve the associated data after the occurrence of event 7.

FIG. 4 illustrates an exemplary table of data tags of events stored in afirst-in-first-out (FIFO) memory 260 in the case where aperturefiltering is enabled in accordance with another embodiment of theinvention. As discussed with reference to the previous example, thecontrol module 218 using the aperture filter 212 and the event filter214 records seven (7) events in the FIFO 216 as noted in the table. Foreach event, the control module 218 records the corresponding x- andy-positions (and z-position or pressure, if applicable), and a tag thatindicates the type of event. For example, tag 00 indicates an initialtouch event of the touchscreen display, tag 01 indicates a notablemid-press event or dragging of the pointer or finger across thetouchscreen display, and 10 indicates a release or removal of thepointer or finger from the touchscreen display. A tag of 11, not shownin this figure, indicates that there is no unread data available for theapplications processor 260.

FIG. 5 illustrates an exemplary table of data tags stored in afirst-in-first-out (FIFO) memory in the case where aperture filtering isnot enabled. Because in this example, aperture filter has been disabled,more mid-press or dragging events are recorded, as noted in the table.This produces much more data transfer to the applications processor 260;thereby reducing the speed and efficiency of the applications processor.

FIG. 6 illustrates a flow diagram of an exemplary method 600 ofinterfacing the applications processor 260 with the touchscreen display250 in accordance with another embodiment of the invention. The method600 may be implemented by the touchscreen controller 210. According tothe method 600, the control module 218 receives configurationinstructions from the applications processor 260 via the interface 222(block 602). The configuration instructions tells the control module 218the measurement criteria and the data logging criteria. For example, themeasurement criteria may specify the frequency or rate in which toperform measurements of the touchscreen display 260, and whatmeasurements to take (e.g., x-position, y-position, z-position orpressure of the touch). The data logging criteria may specify the eventsto record in a memory (e.g., initial touch, mid-press drags that exceeda defined distance, touch release, etc.) With regard to mid-press drags,the control module 218 may receive dimensions for the aperture windowfrom the applications processor 260 via the interface 222.

Then, according to the method 600, the control module 218 then monitors,in a relatively low power mode, the touchscreen display 250 for aninitial touch (block 604). If the control module 218 does not detect aninitial touch of the touchscreen display 250, the control modulecontinues to monitor for the initial touch in the relatively low powermode. If, on the other hand, the control module 218 detects an initialtouch of the touchscreen display 250, the control module performs ameasurement of the touchscreen display 250 (block 606), records themeasurement data and an initial touch event identifier or tag in theFIFO 216 (block 608), and sends an interrupt to the applicationsprocessor 260 via the interface 222 (block 610). The control module 218then waits until the next scan interval (block 612).

Then, in the next scan interval, the control module 218 performs anothermeasurement of the touchscreen display 250 (block 614). Based on themeasurement data, the control module 218 determines whether the user hasperformed a notable mid-press event (e.g., dragging the pointer orfinger across the touchscreen display 250) (block 616). If the controlmodule 218 does not detect a notable mid-press event, the control moduleproceeds to the operation specified in block 622. Otherwise, the controlmodule 218 records the measurement data and mid-press event identifieror tag in the FIFO 216 (block 618), and sends an interrupt to theapplications processor 260 via the interface 222 (block 620). Thecontrol module 218 then waits for the next scan interval per block 612.

If, on the other hand, the control module 218 determines in block 616,that the measurement data does not pertain to a mid-press event, thecontrol module 218 determines whether it pertains to a user removing orreleasing the pointer or his/her finger from the touchscreen display 250(block 622). If the control module 218 determines that it was not atouch release event, the control module proceeds to wait for the nextscan interval per block 612. Otherwise, the control module 218 recordsthe measurement data and touch release event identifier or tag in theFIFO 216 (block 624), and sends an interrupt to the applicationsprocessor 260 via the interface 222 (block 626). Then, the controlmodule 218 proceeds to detecting the next initial touch by the user perblock 604.

FIG. 7A illustrates a flow diagram of another exemplary method 700 ofinterfacing the applications processor 260 with touchscreen display 250in accordance with another embodiment of the invention. According to themethod 700, before a user touches the touchscreen display 250 (TOUCH=0),the control module 218 idles in a touch detect mode (TDM), where it isconfigured to operate in a relatively low power consumption mode tosense the touching of the touchscreen display 250 by the user (block702). If the control module 218 senses the touching of the touchscreendisplay 250 (TOUCH=1), it configures itself in a relatively high powerconsumption mode to perform a measurement of the touchscreen display 250(block 704).

Based on the measurement data, the control module 218 determines whetherit relates to a special event (block 706). For example, the specialevent may include initial touches and touch releases of the touchscreendisplay 250. As previously discussed, the applications processor 260 mayspecify what events are special in the configuration instructions. Inthis example, the control module 218 identified the initial touch of thetouchscreen display 250 as a special event, and thus, logged themeasurement data and event identifier in the FIFO 216 (block 710).Additionally, the control module 218 may send an interrupt to theapplications processor 260 via the interface 222 to inform it that datais available in the FIFO 216 (block 712). Based on the measurementperformed per block 704, the control module 218 determines whether thetouchscreen display is being touched (block 714). In this case, thecontrol module 218 determines that the user is still touching thetouchscreen display 250, and thus, the control module reconfiguresitself in the relatively low power mode until the next scheduledmeasurement cycle (block 716).

In the next measurement cycle, the control module 218 performs anothermeasurement of the touchscreen display 250 (block 704). In this example,the user merely dragged his/her finger or stylus to a different regionof the touchscreen display 250. In such a case, the control module 218may not recognize that event as being a special event pursuant to block706. Accordingly, the control module 218 determines whether themid-press drag exceeds a defined aperture window (block 708). If yes,the control module 218 logs the measurement data and event identifier inthe FIFO 216 (block 710), sends an interrupt to the applicationsprocessor 260 via the interface 222 to inform it that data is availablein the FIFO 216 (block 712), and then proceeds to block 714. On theother hand, if the control module 218, in block 708, determines that themid-press drag did not exceed the aperture window, the control modulethen proceed directly to block 714. In this case, the control module218, in block 714, determines that the touchscreen display is beingtouched based on the measurement taken per block 704, and then proceedsto wait for the next scan cycle per block 716.

In the next measurement cycle, the control module 218 performs anothermeasurement of the touchscreen display 250 (block 704). In this example,the user has removed his/her finger or stylus from the touchscreendisplay 250. Accordingly, the control module 218 determines that thetouch release is a special event (block 706). The control module 218then logs the measurement data and event identifier in the FIFO 216(block 710), sends an interrupt to the applications processor 260 viathe interface 222 to inform it that data is available in the FIFO 216(block 712), and then proceeds to block 714. In block 714, the controlmodule 218 determines that the touchscreen display is not being touchedbased on the measurement taken per block 704, and then it reconfiguresitself in the touch detect mode (TDM) per block 702.

FIG. 7B illustrates a flow diagram of an exemplary method 750 of theapplications processor 250 interfacing with a touchscreen controller 210in accordance with another embodiment of the invention. As discussedabove, because of the data measurement and event recordation of thetouchscreen display 250 is now performed by the touchscreen controller210, the role of the applications processor 260 is merely to receivenotifications as to when data is available for reading, and read thedata at its leisure. Thus, according to the method 750, the applicationsprocessor 260 remains in an idle mode with regards to the touchscreendisplay 250 when the interrupt signal indicates that there is noavailable data (IRQ=0) (block 752). When the interrupt signal indicatesthat data is available (IRQ=1), the applications processor 260 retrievesthe data at its leisure (block 754). If the applications processor 260accesses all of the available data and thus the interrupt signalindicates no more data available (IRQ=0), it returns back to idle mode(block 752). Alternatively, instead of using the interrupt signal, theapplications processor 260 may poll the FIFO memory 216 to determinewhether or not event data is available. As previously discussed, a code(e.g., ETAG=11) may be stored in the FIFO memory 216 to indicate thatthere is no more event data.

FIG. 7C illustrates a timing diagram related to an exemplary operationof the touchscreen controller 210 in accordance with another embodimentof the invention. The top waveform illustrates the user's interactionwith the touchscreen display 250, and namely, in this example, theinitial touch and touch release of the display as noted. The secondwaveform from the top illustrates the operations of the control module218 in performing the display measurement and data collection processes.The third waveform from the top illustrates the state of the interruptsignal IRQ indicating when data is available, and when all the data hasbeen read by the applications processor 260. The bottom waveformillustrates the operation of the applications processor 260 in readingthe data from the FIFO memory 216.

As indicated at the far left part of the diagram, prior to the usertouching the touchscreen display 250 as indicated by the low logic levelof the touchscreen display activity signal, the interrupt signal IRQ isat a low logic level indicating that there is no available data in theFIFO 216, and the control module 218 is in the touch detect mode TDM. Inresponse to the touchscreen display 250 being touched as indicated bythe touchscreen display activity signal transitioning to a high logiclevel, the control module 218 begins performing a measurement scan ofthe touchscreen display 250 after an initial time interval t_(INIT). Thecontrol module 218 scans the touchscreen display 250 for a measurementtime interval t_(MEAS), acquires the measurement data, identifies theevent as an initial touch, and stores the measurement data and eventidentifier (ETAG=00) in the FIFO 216.

After the measurement scan, the control module 218 enters a relativelylow power mode (LPM) for a sample time interval t_(SP) until the nextmeasurement scan. In response to the measurement, the control module 218causes the interrupt signal IRQ to transition to a high logic levelindicating that data is available in the FIFO 216 for access by theapplications processor 260. In this example, the applications processor260 responds relatively quickly to the first indication of availabledata, and reads the data from the FIFO 216 as indicated in the bottomwaveform. In response to the reading of the data, and the FIFO 216 nowhaving no available data, the control module 218 causes the interruptsignal IRQ to transition to the low logic level indicating again thatthere is no available data in the FIFO 216.

After the first sample time interval t_(SP), the control module 218performs another measurement scan of the touchscreen display 250 for asecond measurement time interval t_(MEAS), acquires the measurementdata, identifies the event as a mid-press drag, and stores themeasurement data and event identifier (ETAG=01) in the FIFO 216. Afterthe measurement scan, the control module 218 enters the low power mode(LPM) for another sample time interval t_(SP) until the next measurementscan. In response to the measurement, the control module 218 causes theinterrupt signal IRQ to transition to the high logic level indicatingagain that data is available in the FIFO 216 for access by theapplications processor 260. In this example, however, the applicationsprocessor 260 does not respond quickly to the indication of availabledata as noted by the interrupt signal remaining in the high logic level.

After the second sample time interval t_(SP), the control module 218performs another measurement scan of the touchscreen display 250 for athird measurement time interval t_(MEAS), acquires the measurement data,identifies the event as another mid-press drag, and stores themeasurement data and event identifier (ETAG=01) in the FIFO 216. Afterthe measurement scan, the control module 218 enters the low power mode(LPM) for another sample time interval T_(SP) until the next measurementscan. Since there is still data available in the FIFO 216, the controlmodule 218 maintains the interrupt signal IRQ at the high logic level tostill indicate that data is available in the FIFO 216 for access by theapplications processor 260. Again, in this example, the applicationsprocessor 260 does not respond quickly to the indication of availabledata as noted by the interrupt signal IRQ continuing to remain at thehigh logic level.

After the third sample time interval t_(SP), the control module 218performs another measurement scan of the touchscreen display 250 for afourth measurement time interval t_(MEAS), acquires the measurementdata, identifies the event as a touch release, and stores themeasurement data and event identifier (ETAG=10) in the FIFO 216. Afterthe measurement scan, the control module 218 enters the touch detectmode (TDM) for monitoring the next touch of the touchscreen display 250.Since there is still data available in the FIFO 216, the control module218 maintains the interrupt signal IRQ at the high logic level to stillindicate that data is available in the FIFO 216 for access by theapplications processor 260. In this example, the applications processor260 soon thereafter reads all of the available data in the FIFO 216 asnoted by the interrupt signal IRQ transitioning to the low logic levelto indicate that there is no available data in the FIFO. This exampleillustrates that the applications processor 260 is at will to read datarelated to one or more events from the FIFO 216 at any time as long asthe FIFO does not overflow with data, which may result in loss of data.

While the invention has been described in connection with variousembodiments, it will be understood that the invention is capable offurther modifications. This application is intended to cover anyvariations, uses or adaptation of the invention following, in general,the principles of the invention, and including such departures from thepresent disclosure as come within the known and customary practicewithin the art to which the invention pertains.

What is claimed is:
 1. A method of interfacing a position-indicatingdevice with an applications processor, comprising: sensing a pluralityof events related to a user interacting with the position-indicatingdevice; filtering the events to identify one or more predeterminednotable events; and sending data related to the one or morepredetermined notable events to the applications processor.